956 The American Naturalist. [ November, 
displaced and absorbed by the embryo-sac, which subsequently becomes 
very much enlarged. Sections were made showing a partial oblitera- 
tion of the nucellus, and at this period of growth the embryo-sac is 
completely filled with protoplasm, in the central portion of which is 
located the mother-cell, with a vacuole both above and below it. 
Later sections showed a complete displacement of the nucellus, an 
elongation of the embryo-sac, a further separation of the vacuoles, the 
first division of the mother-cell into two daughter cells, each moving, 
the one to the upper the other into the lower end of the embryo-sae. 
In the next stage of development we have the first division of the 
polar nuclei, thus making two nuclei in each end of the embryo-sac. 
The two upper nuclei rest within an accumulation of protoplasmic 
substance, while the two lower nuclei rest within a less dense plasma 
between an upper and a lower vacuole which show a longitudinal 
expansion. Previous to the last division of the polar nuclei a longi- 
tudinal increase of the whole embryo-sac takes place. Subsequently 
each of the two nuclei divides, and we have four nuclei occupying 
opposite extremities of the embryo-sac. Thus, division is complete, 
and the upper cells give rise to the egg-apparatus, while the lower are 
designated antipodal cells. The next stage of development is charac- 
terized by the ascent of one of the antipodal cells toward the center 
of the embryo-sac. This nucleus is imbedded in a dense mass of pro- 
toplasmic material separating two large vacuoles. Of the three anti- 
podal cells remaining, the two upper of which lie alongside and 
impinge on each other, also rest in a plasma bridge separating two 
vacuoles, the upper of which is the larger, and the lower one of the 
two previously mentioned vacuoles. The lowermost cell is partly 
obscured by the impingement of the lowermost vacuole. 
At the micropylar end of the embryo-sac the cells have a far differ- 
ent significance. One of the cells in its descent toward the center of 
the sac meets its fellow from below and both coalesce, thus forming 
the secondary or endosperm nucleus. The three remaining cells, 
though naked like the three opposite, but surrounded by a dense mass 
of protoplasm, constitute the true egg-apparatus. The two upper cells 
of the egg-apparatus, which lie side by side, occupying the whole 
tapering anterior end of the embryo-sac, are the synergide ; at their 
lower extremity, oceupying nearly the whole width of the sac, lies a 
large rounded cell, the oosphere. 
In further development the embryo-sac becomes very much swollen, 
which is a characteristic feature both before and after the process of 
fertilization. But fertilization in this case has not yet been accom- 
